# Node Polyfill Plugin

import { SourceCode } from 'rspress/theme';

<SourceCode href="https://github.com/web-infra-dev/rsbuild/tree/main/packages/plugin-node-polyfill" />

:::tip About Node Polyfill
Normally, we don't need to use Node libs on the browser side. However, it is possible to use some Node libs when the code will run on both the Node side and the browser side, and Node Polyfill provides browser versions of polyfills for these Node libs.
:::

By using the Node Polyfill plugin, Node core libs polyfills are automatically injected into the browser-side, allowing you to use these modules on the browser side with confidence.

## Quick Start

### Install Plugin

You can install the plugin using the following command:

import { PackageManagerTabs } from '@theme';

<PackageManagerTabs command="add @rsbuild/plugin-node-polyfill -D" />

### Register Plugin

You can register the plugin in the `rsbuild.config.ts` file:

```ts title="rsbuild.config.ts"
import { pluginNodePolyfill } from '@rsbuild/plugin-node-polyfill';

export default {
  plugins: [pluginNodePolyfill()],
};
```

## Node Polyfills

### Globals

- `Buffer`
- `process`

When you use the above global variables in your code, the corresponding polyfill will be automatically injected.

For instance, the following code would inject the `Buffer` polyfill:

```ts
const bufferData = Buffer.from('abc');
```

You can disable this behavior through the `globals` option of the plugin:

```ts
pluginNodePolyfill({
  globals: {
    Buffer: false,
    process: false,
  },
});
```

### Modules

- `assert`
- `buffer`
- `console`
- `constants`
- `crypto`
- `domain`
- `events`
- `http`
- `https`
- `os`
- `path`
- `punycode`
- `process`
- `querystring`
- `stream`
- `_stream_duplex`
- `_stream_passthrough`
- `_stream_readable`
- `_stream_transform`
- `_stream_writable`
- `string_decoder`
- `sys`
- `timers`
- `tty`
- `url`
- `util`
- `vm`
- `zlib`

When the above module is referenced in code via import / require syntax, the corresponding polyfill will be injected.

```ts
import { Buffer } from 'buffer';

const bufferData = Buffer.from('abc');
```

### Fallbacks

- `child_process`
- `cluster`
- `dgram`
- `dns`
- `fs`
- `module`
- `net`
- `readline`
- `repl`
- `tls`

Currently there is no polyfill for the above modules on the browser side, so when you import the above modules, it will automatically fallback to an empty object.

```ts
import fs from 'fs';

console.log(fs); // -> {}
```

## Options

### globals

Used to specify whether to inject polyfills for global variables.

- **Type:**

```ts
type Globals = {
  process?: boolean;
  Buffer?: boolean;
};
```

- **Default:**

```ts
const defaultGlobals = {
  Buffer: true,
  process: true,
};
```

### protocolImports

Whether to polyfill Node.js builtin modules starting with `node:`.

- **Type:** `boolean`
- **Default:** `true`

For example, if you disable `protocolImports`, modules such as `node:path`, `node:http`, etc. will not be polyfilled.

```ts
pluginNodePolyfill({
  protocolImports: false,
});
```
